Combustion speed

For code R8 it commences with a solid with the help of AFNOR standards NF T 20-035 . Handling consists in preparing mixtures of variable compositions of an oxidant to be classified as cellulose. Both substances have to have a definite particle size distribution. The composition which gives the fastest combustion on a moulding of the mixture at a distance of 20 cm is established. This speed is compared with the one of the mixture used as a reference, which has an imposed composition of barium nitrate and cellulose. If the combustion speed of the particular substance is higher than that of the reference, it will bear R8. 

Fig. 1 Dependence of the normal combustion speed of CO on the concentration of CCI4.

To be detected by AAS, the analyte must be presented to the optical beam of the instrument as free atoms. The process of converting analyte ions/molecules, dissolved in a suitable solvent, to gaseous atoms is accomplished by the nebuliser flame assembly. The nebuhser (from the Latin nebula meaning cloud) creates an aerosol (a fine mist) of the hquid sample which is mixed with an oxidant gas and a fuel gas (to support the flame combustion). The mixture is ignited above the burner assembly. The liquid droplets are desolvated, the resulting microcrystals are melted and vaporised and finally the gaseous products are thermally dissociated to produce free atoms. The combustion speed of most flames is such that the conversion from liquid droplet to free atoms must be accomplished within a few milhseconds. 

Combustion process has stable and unsteady combustions. The stable combustion of explosives presents that single component explosive has a constant burning/ combustion speed under certain conditions (e.g., fixed pressure, temperature, packed density, etc.). Most of liquid explosives can reach stable combustion. The combustion of explosive is not always stable. For mixed liquid explosives, the combustion speed may accelerate or slow down, sometimes accelerate or slow down suddenly. The main reason is the nonuniformity of mixtures. 

Acceleration of unsteady combustion leads to faster combustion, finally detonation. Slowing down results in flie slower combustion, to burning off. Whether an explosive explodes finally is determined by its combustion speed. 

According to the equation of evaporation-combustion, the mass combustion speed of evaporation is Eq. 2.7. 

If the combustion is the first-order reaction, the mass combustion speed of volatile explosives is written in Eq. 2.8. 

In stable/steady combustion, the combustion speed of liquid explosives has a relationship of Eq. 2.18 with pressure. 

Fig. 2.3 The relation plots of combustion speed of H202-azidoethane mixture and the pressure. 1 H202-azidoethane 2 N204-unsym-dimethylhydrazine 3 Mercury fulminate 4 Nitroglycerine 5 hexogen...

As discussed in Chapter 1 (Introduction to Pyrolants), metal-fluorocarbon pyrolants possess the highest volumetric combustion enthalpies among energetic materials. In addition, the combustion speed of metal-fluorocarbon pyrolants can be easily adjusted as well. Thus, these materials may be applied in situ as a heat source to volatilise or decompose other materials to generate aerosols. 

The interpretation of the TVA results also allows studying the corrosion and oxidation behavior in controlled atmospheres at a very wide range of temperature or combustion speeds, as well as the distillation, evaporation, and sublimation of the material [17]. 

HB the lowest rating where the combustion speed is less than 38 mm/min. 

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